Automatic control circuit for discharge lamps



March 15, 1960 L. F. BIRD 2,928,989

AUTOMATIC CONTROL CIRCUIT FOR DISCHARGE LAMPS Filed Nov. 15, 1957 INVENTQR [Ears/P 56 /60 BY KM HA1 ATTORNEYS United States Patent 6 AUTOMATIC CONTROL CIRCUIT FOR DISCHARGE LAB HE'S Lester F. Bird, Newark, N.J., assignor to Engeihard Industries, Inc., a corporation of New Jersey Application November 15, 1957, Serial No. 696,809

1 Claim. (Cl. 315-90) The present invention deals with a control circuit for discharge lamps and more particularly with an automatic control circuit for operating a dual discharge lamp system.

It is an object of the present invention to provide a dual discharge lamp system and an automatic control circuit therefor, whereby a lamp of one system will automatically ignite when a lamp of the other system fails to operate. Other objects and advantages of the invention will become apparent from the description hereinafter following and the drawing forming a part hereof.

The drawing is a diagrammatic illustration of a dual discharge lamp system according to the invention.

The invention deals with a dual discharge lamp system operated by an automatic control circuit such that when a lamp of a first system fails to operate, a lamp of a second system will automatically ignite and at the same time cause a remotely located signal lamp to light as a signal that the second system lamp is in operation.

Regarding the illustration, supply leads 1 and 2 are connected to a source of, for example, 60 cycle supply voltage of about 115 volts. A series iron cored reactor 3 is connected into one of the supply leads, e.g. lead 1. The other supply lead, e.g. lead 2, is connected to a terminal of primary winding 4 of a step-up transformer 5. The reactor 3 is connected to the other terminal of the primary 4 by conductor 6, and a discharge lamp 7 is connected across the terminals of the secondary winding 8 of transformer by means of conductors 9 and 10. The reactor 3 has a reactance such that all but about 25 volts will be consumed when the lamp 7 is ignited and current flows through the reactor. The transformer 5 is of the leakage type having built-in reactance between its primary and secondary windings.

In combination with the circuit above described, a second transformer 11 is employed with one terminal of its primary winding 12 connected to the supply lead 2 by conductor 13, the other terminal thereof being connected to the conductor 6 by another conductor 14. The secondary winding 15 of transformer 11 is connected across a second discharge lamp 16 through the common conductor 10, or its equivalent, and by conductor 17 to the other terminal of secondary winding 15, through a series autotransformer 18 connected in the conductor 17 in series with the lamp 16.

In accordance with the invention, the transformer 15 is similar to transformer 5, but has a reduced step-up ratio compared with transformer 5. The primary winding 4 of transformer 5 and the primary winding 12 of transformer 15 are in parallel so that whatever voltage exists across the transformer primary 4 also exists across the primary winding 12.

The lamps 7 and 16 are, for example, lamps of the usual discharge type, such as tubular lamps containing electrodes and a filling of neon, or lamps of the mercury 2,928,989 Patented Mar. 15, 1960 discharge type having a fluorescent coating on the lamp envelope. Other types of lamps are also contemplated.

Upon application of voltage to the circuit through the supply leads 1 and 2, and before ignition of either lamp, the current drawn by the primary windings 4 and 12 is small and there is not much reduction in the voltage supplied to the primary windings through the reactor 3. The voltage across the primary windings 4 and 12, when no lamps are lighted, is about or more volts. With 75 volts on the primaries 4 and 12, there is sufficient voltage delivered through the secondary windings 8 and 15 to operate the lamps under any conditions. However, immediately after one lamp is lighted, the load on its transformer increases the current requirements and so increases the reactor drop, whereby the input voltage to the transformer is reduced accordingly, e.g. to about 25 volts. As soon as the first lamp 7 ignites, the input voltage to the second transformer 11 is reduced, as a result of the function of reactor3, and there is insuflicient voltage available to lamp 16 from transformer 11 to ignite it. For this reason the second lamp 16 remains out as long as the first lamp 7 is operating. However, should the first lamp 7 fail to ignite for any reason, even for a single cycle, the voltage across the transformer primaries rises to the ignition point for the second lamp 16 and it operates instead. In this manner the two lamps will opcrate together with one always lighting first and the other serving as a standby awaiting the time when the first lamp will no longer serve.

Having provided the dual lamp circuit above described, it is advantageous to indicate, at a remote point, that the standby lamp 16 is in operation. For this purpose there is provided a signal lamp 19 connected across the primary winding 20 of transformer 21, with the secondary Winding 22 of transformer 21 being connected across the autotransformer 18 by conductors 23 and 24. The purpose of transformers 18 and 21 is to provide the small signal lamp with the proper voltage and current which would not be available to it by direct connection to conductor 17 feeding the lamp 16.

While the invention is described in relation to the specific circuit illustrated, modifications are contemplated within the scope of the appended claim.

What is claimed is:

An automatic control circuit for a dual discharge lamp system, comprising supply leads, a series reactor in at least one of the supply leads, a first reactive type transformer having primary and secondary windings, a first discharge lamp connected across the secondary winding, the primary winding being connected in series with the reactor, a second reactive type transformer having primary and secondary windings, a second discharge lamp connected across the secondary winding of the second transformer, the primary winding of the second transformer being connected in series with the said reactor and in parallel with the primary winding of the first transformer, the transformers having diiferent step-up ratios.

References Cited in the file of this patent UNITED STATES PATENTS 2,075,606 Foerste Mar. 30, 1937 2,076,278 Ryde Apr. 6, 1937 2,292,064- Dorgelo Aug. 4, 1942 2,460,979 Foerste Feb. 8, 1949 2,514,753 Freeman July 11, 1950 2,611,885 Bridges Sept. 23, 1952 2,809,329 Stier Oct. 8, 1957 

